Bell-shaped illuminating device



July 15,1930.

w. 'BAIJERSFELD,

BELL SHAPED ILLUMINATING DEVICE Fired Jan. 4, 1 92"! amm w WM M ' Patented July 15, 1930 7 UNITED STATES,

PATENT OFFICE WALTHER BAUERSFELD, OF JENA, GERMANY, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO ZEISS IKON A.-G., GOERZWERK, F BERLIN,

GERMANY BELL-SHAPED ILLUMINA'IING DEVICE Application filed January 4, 1927, Serial No.

of light to beused with the mirror (e. g. a glow lamp), Whose dimensions are fixed. ccording to the present invention a comparatively small aperture is also attained for 20 small angles of the luminous field owing to the fact that the zones of the mirror are at any one time displaced relatively to the adjacent smaller zones towards the mirror axis. The mirror may be com osed of single con-7 2 structional parts, each 0? one zone, ter case it is necessary, in order to connect the zones to each other, to provide connecting surfaces for the selection of which it is 80 decisive that the loss of light connected therewith shall beconfined to the smallest possible amount. According to the invention this is attained by uniting the zones by means of spherical surfaces locus of the source of light.

rays incident on these connecting surfaces are thereby reflected in the direction of incidence and again act in such a way as if they direct- 0 1y emanated (only weakened by the loss, of

- absorption) from the source of light. In or-' der to avoid any further unnecessary loss of absorption it must be seen to that the rays, afterhavingbeen reflected, do not strike again coInInecting but zonal surfaces whicih may be ac 'evedby imparting to the e zones at corresponding width. In this i ganner the said rays join'in the shortest way the i1 laminating pencil radiated by the mirror. The annexed drawing shows in a construcadjacent must yet admit of an unrestricted introduction of the source which represents or consist of one piece. In the latwhose centres lie at the The luminous P 158,979, and in Germany January 22, 1926.

tional form an example of the new illuminatlng device in a cross section.

he mirror, which may consist of plateglass or metal, contains zones a a united by connecting surfaces 6 b Theseconnecting surfaces '6 b .form themselves spherical surfaces whose centre 0, which is assumed to be the locus of the source of light, lies on the axis 03' ofthe mirror' which axis thus simultaneously forms the axis of the radiated pencil of lumi- The width of is so chosen that .luminous rays 6 e striking the connecting surfaces 6 6 are thrown on the way denoted by' arrows f, f onto the surfaces of the zones a a Where they undergo their second and last deflection.-

I claim:

Bell-shaped illuminating device comprising a source of light and a mirror, the reflecting surface of which is composed of zones displaced relatively to each other like ste nous rays.

source of light, the zones running round the axis of the mirror on the whole circumference, l l

being connected with each other by spherical surfaces whose centres-coincide at a point of the mirror axis and the zones ofthe mirror. being of such construction that always opite one spherical surface with regard to its centre lies one of the said zones.

WA LTHER BAUERSFELD.

the zones a a c5 sand directed towards the source of lig t so as to reflect light emanated from the acent smaller axis, the zones so 

